Techniques of transferring data using packets are applied to various fields. Transmission Control Protocol/Internet Protocol (TCP/IP) is a technique for transferring packets of data over the Internet. PCI Express® is a technique for transferring packets of data between integrated circuits. NoC (Network-on-Chip) is a technique for transferring packets of data within an integrated circuit. In the techniques for transferring packets of data, various types of data necessary for transferring an address or data can be transferred with a small number of signal lines. For example, in PCI Express®, data can be transferred using only two pairs of differential lines. In addition to the feature of a small number of signal lines, such techniques can increase transfer rates. However, in the packet-based transfer techniques, since various types of information are arranged to be sent in a time domain, the number of cycles necessary for transferring the data is larger than that in non-packet-based transfer techniques. To solve the problem, there have been proposed techniques for minimizing information transfer with an advanced packet structure to reduce the number of cycles necessary for data transfer, and thereby to increase the transfer efficiency. For example, a header compression method by V. Jacobson specified in RFC 1144 (RFC 1144, “Compressing TCP/IP Headers”, February 1990) is provided. In the header compression method by V. Jacobson, packets transferred last are compared with packets to be transferred next, and then only the difference information is transferred so that packets can be compressed to improve the transfer efficiency.